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Subject: Battlezone high score upgrade (LONG) Date: 23 Jun 1994 12:06:29 GMT Organization: Texas Instruments Lines: 365 Distribution: world Message-ID: <2ubts5$> NNTP-Posting-Host: Well I finally got my Battlezone permanent high score fix working, thanks to the 48Z02 datasheet that Clive Bittlestone sent (the chip has 2 chip enables that do not behave the same, and I was using the wrong one, so I swapped a couple of wires and bingo). Also thanks go to Doug Jefferys and all the other folks that sent me ideas for future improvements and alternative ways to preserve the high scores. I'd be interested in any feedback folk have. Problems? Praise? .... whatever, so I can make adjustments to this document. Regards, John. * John Keay ! Texas Instruments Ltd. * * ! Bedford, U.K. * * Disclaimer: All opinions expressed herein are personal. etc etc * ----------------------------------------- UPGRADE: Battlezone Permanent high score. ----------------------------------------- AUTHOR: John Keay WRITTEN: June 1994 DISCLAIMER ---------- The opinions expressed within this document are those of the author only and not necessarily those of the author's employer. This document is provided for informational purposes only. Although the author has made every effort to provide accurate information, he cannot guarantee the accuracy or usefulness of any of the information contained herein due to the complexity of the issues involved. The author takes no responsibility for anything arising as a result of anyone using the information provided in this document, and the reader hereby absolves the author of any and all liability arising from any activities resulting from the use of any information contained herein. THE UPGRADE ----------- This upgrade will allow Battlezone high scores to be remembered while the machine is switched off. Simple as that. The upgrade needs no special intervention by the user after the upgrade has been installed and the machine has been powered up once. The upgrade has been designed so the machine only saves the top 5 highscores (so mere-mortals can get on the score sheet occasionally). It has also been designed so that the saved high scores can be cleared out by reseting the machine with one of the coin switches held down. The fix is implemented by replacing Battlezone's existing program RAM with battery-backed-ultra-lower-power-CMOS-SRAM. Then a new EPROM can be blown that will convince Battlezone not to initialize the area of this RAM that is used for the high scores (unless the operator wants this to happen). The batteries in the zero-power replacement SRAM we are going to use should last about 10 or 20 years, so your highscores will be safe for quite a while. Read these detail through a couple of times, if you plan to do the fix, because I haven't always got things in exactly the correct order. "...and now Sir Launcelot, Sir Galahad and I jump out of the rabbit....." :-) THE DETAILS ----------- I rate this upgrade "easy-ish" on a scale of "trivial" to "impossible", but please take infinite care when upgrading, Battlezone is a machine that is close to my heart (number 2 on the all-time greats list IMHO) and I'd hate to hear about *ONE* functional machine not recovering from the "upgrade". As half the fix is a software patch there is enless scope for different variations, but I will stick to just one example with more patches to follow later. This means you will need access to an EPROM programmer to use the upgrade. Here is the parts list: Number Part list ------ --------- 1 2716 - 2K x 8 EPROM 1 MK48Z02 - 2K x 8 Zero power (TM) SRAM. 1 24-pin DIL socket 2 18-pin DIL socket The most expensive part was the zero powered SRAM cost which me about 6 pounds ($9). First I'll describe the hardware change and then I'll talk about the software change. HARDWARE -------- Firstly we need to disable the two static RAMs that Battlezone currently uses as program RAM (as we are going to install some more and we don't want them fighting it out). 1) Socket H2 & J2. The 2 RAMs in question are 2114s at locations H2 & J2 on the Battlezone CPU board (the larger one with the reset button). I desoldered these chips and installed sockets (but you can disable them anyway you like). Remember to be very careful desoldering chips from these old boards because the wire tracks on the board have a tendency to peel away from the board (as I rediscovered to my horror and I had to add a jumper wire or two). This is the hardest stage of the fix so take your time so you don't damage the board. You will need access to pins 8 & 10 at either H2 or J2 later so if you disable the chips some other way bare that in mind. Once you have removed the 2114s solder in 2 new 18 pin sockets, insert the original 2114s and re-test your board in the machine. Everything OK? This might be a good time to ensure the Battlezone power supply is producing greater than 4.75V. Adjust the small trim pot of the Audio card if it isn't. The new SRAM we are going to install will protect itself if the voltage is too low. 2) Piggy-back socket on EPROM. The next stage is to solder a socket to the back of the replacement 2716 eprom chip that we are going to use to replace the PROM at location N1 (it should be labelled 036-409 or something). It is best if the ROM has already been programed with the new data as detailed below. Not all the pins on the socket should be connected to the EPROM. Also find a socket with a hole in the centre (or you wont be able erase the EPROM to change to patch without de-soldering things). If your EPROM eraser has enough head room you should have no problem erasing and programming the EPROM even with the socket attached. Socket from above 1 |O|---U---|O| 24 Socket and eprom from side 2 |O|-------|O| 23 3 |O| |O| 22 +--------------+ 4 |O| |O| 21 R/W | | socket 5 |O| Hole |O| 20 Gbar +--------------+ 6 |O| here |O| 19 A10 |||||||||||| Solder most pins together 7 |O| |O| 18 Ebar +--------------+ 8 |O| |O| 17 | | eprom 9 |O| |O| 16 +-||||||||||||-+ 10 |O| |O| 15 |||||||||||| 11 |O|-------|O| 14 12 |O|-------|O| 13 Blow-up of socket to eprom connection .......----------+ | |Socket | .......----++----+ || .......----||----+ \/ | Solder here------> __ | EPROM | | | .......---\ /---+ || || \/ Pins 18/19/20/21 on the socket are not soldered straight through. Bend these pins up before you solder the rest to their corresponding EPROM pin. I used some connection wire to connect pins 19 and 20 round (not over) to pin 12 (GND) on the socket. I also used 2 lengths of single core wire (so I could insert one end into a socket) to connect pins 18 and 21 to one of the now vacant 2114 sockets at H2 or J2. In summary: Socket pin Connected to ---------- ------------ 18 (Ebar) pin 8 on socket H2 or J2 (this is the RAM select). 19 (A10) ground 20 (GBar) ground 21 (R/W) pin 10 on socket H2 or J2 (this is the read/write signal). 3) Plug and play. Assuming you have patched the EPROM, all you have to do now is plug and play. - Carefully remove the PROM in socket N1. - Plug the EPROM with a socket on its back into N1. - Connect the 2 single core jumper wires to the vacant H2 or J2 sockets. - Insert the 48Z02 into the socket (on the back of the EPROM) at N1. - Hold down the right coin slot switch (to reset the scores) and switch the machine on. Is it still working? - Wait for the monitor to warm up. :-) Is it working? The patch described in this release of the document, should start off with a high score of 0000 and the entire high score table should be blank. If that seems OK have a few games and check things still work OK and that the top few scores are remembered when the power is off. Put the old 2114's and/or the EPROM back in if you have any problems to help isolate the problem. SOFTWARE -------- Now for the software fix. Fortunately all the code that needs patching is in one ROM. Unfortunately I have no intentions of broadcasting ATARI code across the net (for the obvious reasons), so you will have to make do with just the changes, and find a way to edit them into your own binary file of the ROM. OK here is the patch, in a weird format I just invented. :-) 7800 7FFF 7b58 { A2 00 AD 00 08 29 01 F0 02 A2 3C A9 00 9D 00 03 E8 D0 FA A2 0F 9D 0E 03 9D 2C 03 CA D0 F7 20 1F 53 4C 00 50 } 7AE6 { EA EA EA } There are several ways you can patch the binary image, once it has been read from the original 036-409. I loaded the code into a memory monitor tool and edited the changes in by hand then saved it out, but it is simple enough to write a simple perl or C program to automatically do the changes (and I have code in both those languages available if you get completely stuck). Some editors also allow you to edit binary data in hex, this is also an ideal way to do the change. ROM 409 represents the code between addresses 0x7800 - 0x7FFF, so the new data needs to be entered starting at 0x7B58 and 0x7AE6 (which is therefore 0x358 and 0x2E6 bytes from the start of the file). e.g 0x7B58 needs to be set to 0xA2 0x7B59 needs to be set to 0x00 etc.... The first 2 lines contain the start and end addresses of the 036-409 ROM. Next is a list of bytes to be placed at certain locations. ------------- patch for 036-409 --------------------- 7800 <---- start location for ROM 409 7FFF <---- end location for ROM 409 7b58 { <---- 1st lot of changes start here. A2 00 AD 00 08 29 01 F0 02 A2 3C A9 00 9D 00 03 E8 D0 FA A2 0F 9D 0E 03 9D 2C 03 CA D0 F7 20 1F 53 4C 00 50 } 7AE6 { <---- another lot of changes start here EA EA EA } ----------------------------------------------------- That is about all you need to know about the patch. However here are all the gory details for those that are interested. 7ae6 ea NOP ; don't clear page 3 7ae7 ea NOP ; don't clear page 3 7ae8 ea NOP ; don't clear page 3 7b58 a2 00 LDX #$00 7b5a ad 00 08 LDA SWITCH 7b5d 29 01 AND #$01 ; Is right coin switch down? 7b5f f0 02 BEQ L7b63 ; branch if is 7b61 a2 3c LDX #$3c 7b63 a9 00 L7b63 LDA #$00 7b65 9d 00 03 L7b65 STA hiscore,X ; clear all or most of page 3 7b68 e8 INX 7b69 d0 fa BNE L7b65 7b6b a2 0F LDX #$0F ; number of bytes to clear 7b6d 9d 0E 03 L7b6d STA D30E,X ; clear score 7b70 9d 2C 03 STA D32C,X ; clear initial 7b73 ca DEX 7b74 d0 f7 BNE L7b6d 7b76 20 1f 53 JSR init34X ; carry on as before 7b79 4c 00 50 JMP L5000 ; carry on as before .... .... 7b9d Free space down to this location (inclusive). The top ten scores are each stored in 3 BCD bytes starting at location 0x0300 in the RAM (the score is multiplied by 1000 when it is displayed). This section is then followed by the top ten initials (3 bytes each). 0x300 Score 1 0x303 Score 2 0x306 Score 3 .... 0x31B score 10 0x31E Initials 1 0x321 Initials 2 .... 0x339 Initials 10 KNOWN PROBLEMS -------------- The main problem with this patch is that I haven't had a look at the test mode code yet, and because the data in ROM 409 has been changed the Battlezone test mode spots this and complains. This will not effect normal operation but if you put the ROM into test mode you will have problems. I may just be a case of juggling the checksums for the ROM so they match the original ones, or it may be more complicated. Also the test mode might mess with our score locations (while it is testing the RAM). I'll be looking into this problem and will post a new patch that will pass test mode when I've figured it out (or someone has beaten me to it). Until then simply don't enter testmode. If you really need to check things out then put the original ROM (and SRAM) back in first. BATTERY LIFETIME ---------------- The 48Z02 spec says the lifetime of the battery is almost independent of the amount of time the chip is its backup mode. The lifetime is dependent solely on the temperature. An average chip will have a battery lifetime of 20 years at 70 degrees C. Also 99% of chips will have a lifetime of 11 years at 70 degress C. THE FUTURE ---------- There are loads of possibilities for future enhancements that I have discussed with various folks. *) I still had about 30 bytes ROM space left over after the fix, and it would be possible to use this space to initialize the lower scores to something other than zero. I quite liked the blank zero entries so I left it that way. *) Rather than the top 5 scores being reset, the user could select how many scores are saved using the DIP switches. Unfortunately there aren't enough spare switches in Battlezone, but we could hi-jack the language setting switches (which would also free up buckets of ROM space). *) As *ALL* the Program RAM is saved, it might be possible in implement a pause game feature. You could switch your machine off and then resume when it was switched back on again. *) Remember the address line A10 on the new SRAM? We tied it to gnd? Well it is probably possible to tie the pin straight through and double the amount of program RAM available for future patches. The decode appears to be alright and there appears to be room in the memory map but I haven't tried it yet. *) What other games could do with a similar fix? Well if you send me the schematics :-) who knows what we might be able to do. I tried to make the fix described above as general as possible by explaining each stage in detail, but it's not easy to do when describing a specific fix. Hopefully there may be very similar fixes for other boards. I for one would be interested to hear what other boards people manage to apply this principle to. "Share and enjoy" * John Keay ! Texas Instruments Ltd. * * ! Bedford, U.K. * * Disclaimer: All opinions expressed herein are personal. etc etc *


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